Polyolefins, particularly polyethylene, can be crosslinked by first making the resin hydrolyzable, which is accomplished by adding hydrolyzable groups to the resin structure through copolymerization or grafting. For example, ethylene can be copolymerized with an ethylenically unsaturated compound having one or more --Si(OR).sub.3 groups wherein R is a hydrocarbyl radical or the silane compound can be grafted to the resin in the presence of an organic peroxide. The hydrolyzable resins are then crosslinked by moisture in the presence of a silanol condensation catalyst.
The moisture curable polyethylene can be prepared by a single step process, which typically involves introducing all of the components, i.e., the resin, usually in the form of pellets; the unsaturated alkoxysilane; an organic peroxide; a silanol condensation catalyst; an antioxidant; and other additives, into an extruder; mixing the components together; heating until the hydrolyzable group is grafted to the resin; and extruding a molded product, such as a pellet, through the die.
Unfortunately, many of the present moisture curable resin compositions, when converted to typical end products such as power cable insulation, jacketing or semiconducting shields, suffer from inferior heat endurance, poor thermal aging resistance, and yellowing